USA has more big cities than other countries in comparision. That is why those cities receive a lot citizen and tourist. Flight departures of big cities like New-York, Dallas, Chicago and San Francisco are always being in heavy condition.
If we look at the picture we can easily see the average delays in flights. Between 1996 and 2000 Chicago and New York has much more average delay in minutes relatively others. Their flight delays approximately around 30 minutes. But that period San Francisco was reached less statistic numbers in average delays. That average delay was been less than 10 minutes.
Now we see the average delay on 2001-2005 period. This time New York replaced Chicago and it was a first place. Average delay in flight departures of New York more than 30 minutes. In order Dallas was been near to New York. But San Francisco was has been too intensive on that year period. It owns little more from 10 minutes.
2006 and 2010 period is interesting, because when we look at the statistics San Francisco was lose its intensivety. They reach more than 25 minute delay in average flight departure. In other hand New York was used to settled top of delays again. Other interesting fact is Dallas was not given up, their statistic average minute fell from estimated 25 to less than 10 minutes.
The last statictics of table contain 2011 and 2015. During that period numbers was changed but ranking remain same. New York was a number one and San Francisco behind of it, like we used to. Dallas was dropped its delay again and Chicago remain between 10-20 minutes in flight departure.